1. Field of the Invention
The invention relates to monocrystalline bodies and somewhat more particularly to an apparatus for pulling monocrystalline ribbon-like bodies from a molten crystalline film.
2. Prior Art
In semiconductor technology, various processes are known for pulling semiconductor crystals or insulating material crystals from an appropriate melt with the aid of a seed crystal. Generally, it is desirable to pull such crystals into the geometric shape which is to be assumed by a semiconductive or insulating component during the production process of such component. For example, a process of this type is suggested in "Physica Status Solidi", Vol. 27, 1975, pages 231-241. The process described in the foregoing article apparently allows the production of silicon ribbons of about 0.5 mm in thickness by using a graphite die having a capillary tube extending therethrough and employing more or less conventional crystal pulling technology based on capillary action. "Material Research Bulletin", Vol. 6, 1971, pages 571-580 describes further embodiments of this type of process wherein sapphire filaments are pulled from a molten sapphire film positioned on an end surface of a capillary die component through which a capillary tube extends, with a lower end of the tube being in contact with the melt reservoir and the upper end of the tube being open for contact with a seed crystal. The shape of the upper end surface of the capillary die or profiling component determines the shape of the pulled crystal. By appropriately selecting profile components having a desired end surface, one can pull crystals of such desired shape, for example, tubular, filament or ribbon.
In accordance with the prior art suggestions, capillary dies useful for pulling sapphire crystals are composed of molybdenum, tungsten or iridium while capillary dies useful for pulling silicon crystals are composed of graphite.
However, the practice of the above-described process, which is sometimes referred to as the "EFG-process" ("edge-defined, film-fed growth process"), to produce monocrystalline bodies, such as of silicon, yields a very large number of crystal disturbances or imperfections and crystal doping so that it is currently preferable to utilize other processes for producing monocrystals, such as composed of silicon.